netfilter: nf_tables: fix *leak* when expr clone fail

When nft_expr_clone failed, a series of problems will happen:

1. module refcnt will leak, we call __module_get at the beginning but
   we forget to put it back if ops->clone returns fail
2. memory will be leaked, if clone fail, we just return NULL and forget
   to free the alloced element
3. set->nelems will become incorrect when set->size is specified. If
   clone fail, we should decrease the set->nelems

Now this patch fixes these problems. And fortunately, clone fail will
only happen on counter expression when memory is exhausted.

Fixes: 086f332167d6 ("netfilter: nf_tables: add clone interface to expression operations")
Signed-off-by: Liping Zhang <zlpnobody@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 10 insertions, 6 deletions

diff --git a/net/netfilter/nft_dynset.c b/net/netfilter/nft_dynset.c
index bfdb689664b0..31ca94793aa9 100644
--- a/net/netfilter/nft_dynset.c
+++ b/net/netfilter/nft_dynset.c
@@ -44,18 +44,22 @@ static void *nft_dynset_new(struct nft_set *set, const struct nft_expr *expr,
 				 &regs->data[priv->sreg_key],
 				 &regs->data[priv->sreg_data],
 				 timeout, GFP_ATOMIC);
-	if (elem == NULL) {
-		if (set->size)
-			atomic_dec(&set->nelems);
-		return NULL;
-	}
+	if (elem == NULL)
+		goto err1;
 
 	ext = nft_set_elem_ext(set, elem);
 	if (priv->expr != NULL &&
 	    nft_expr_clone(nft_set_ext_expr(ext), priv->expr) < 0)
-		return NULL;
+		goto err2;
 
 	return elem;
+
+err2:
+	nft_set_elem_destroy(set, elem, false);
+err1:
+	if (set->size)
+		atomic_dec(&set->nelems);
+	return NULL;
 }
 
 static void nft_dynset_eval(const struct nft_expr *expr,